1. Field of the Invention
The present invention relates to an endoscope system, and more particularly to an endoscope system capable of supplying a driving signal of an appropriate voltage level to an image pickup section.
2. Description of the Related Art
An endoscope system which is provided with an endoscope that picks up an image of an object inside a subject to be examined, a processor that generates an observation image of the object whose image has been picked up with the endoscope, and the like has been widely used in medical fields and industrial fields.
A processor generates a driving signal for driving an image sensor provided in an image pickup section of an endoscope, and supplies the generated driving signal to the image sensor. For example, Japanese Patent Application Laid-Open Publication No. 2013-165772 discloses an endoscope apparatus that is capable of supplying a driving signal having an appropriate voltage level from an image pickup control section to an image pickup section.
In recent years, a driving signal has a higher frequency in accordance with increasing pixels of image sensors. In addition, in recent years, due to a reduction in a diameter size and an increase in a length of a cable, when a driving signal is transmitted to an image pickup section provided at a distal end portion of an insertion portion, there is a case where the amplitude of the driving signal attenuates and the voltage of the driving signal is below an input lower limit voltage of an image sensor.
Therefore, it can be considered that a cable driver in a processor generates a driving signal having a voltage higher than an input upper limit voltage of an image sensor, to input the generated driving signal to the image sensor through a diameter-reduced and lengthened cable. In this case, the amplitude of the driving signal whose voltage is higher than the input upper limit voltage of the image sensor is attenuated due to transmission through the cable, and therefore the driving signal meets the input voltage standard when the driving signal is inputted to the image sensor.
As described above, in order to output the driving signal that meets the input voltage standard to the image sensor, if the driving signal is generated at a voltage value higher than the input upper limit voltage value with respect to the image sensor in anticipation of the attenuation amount due to the transmission of the driving signal through the cable, the DC voltage to be inputted to the image sensor when the power source of the processor is turned on or off is maintained at a voltage value higher than the input upper limit voltage of the image sensor.